1. Field of the Invention
The present invention relates generally to printing presses and more particularly to a folder of a printing press.
2. Background Information
Web printing presses print a continuous web of material, such as paper. In a folder of the printing press, the continuous web then is cut into signatures in a cutting unit and folded.
One way to fold the resulting signatures is using a rotary blade folder, which includes a folding cylinder with tucker blades which provide a fold to the signature. The fold is forced by the tucker blade toward two rotating fold rolls, which grip the signature along the fold at a nip, set the fold and deliver the folded product, for example, to a fan unit.
Chapter 6 (pages 136 to 154) of the book xe2x80x9cNewspaper Pressesxe2x80x9d by William Braasch describes the two basic kinds of rotary blade folders: 2 to 1 folders and 3 to 2 folders. In a 2 to 1 rotary blade folder, two sets of tucker blades are spaced 180 degrees apart on the folding cylinder. A signature is held by pins spaced 90 degrees ahead of a tucker blade set and when the signature midpoint reaches the fold rollers, the tucker blade pushes the signature at the midpoint into the fold rollers so as to form the fold. Thus in a 2 to 1 folder, two sets of pins spaced 180 degrees apart are present, for holding edges of the products to be folded. In a 3 to 2 folder, three sets of pins spaced 120 degrees apart are present. Sets of tucker blades operate at a midpoint of a signature to produce a fold by pushing the midpoint into a pair of fold rollers.
In order to increase a page count of a product, folders in a printing press utilize a method of collecting sheets to form a larger product. To accomplish the collection of sheets, a tucker blade is silenced so that it does not perform a tucking operation into nip rollers and the pin holding the lead edge of the signature is not retracted. The silencing, which occurs in collect mode, permits the product to remain on a folding cylinder so that the folder is supplemented with additional sheets as a result of the folding cylinder rotating another revolution. When two sheets are collected by the cylinder, the two sheets may then be released by the pin and folded by the tucking blade. The collect mode is in contrast to the straight mode during which no folding blades are silent and no products are permitted to remain on the cylinder, so that each pin retracts every revolution. The switch from collect mode to straight mode or vice versa is called a changeover.
One way to move the pins on the rotary blade folder is with a rotating box cam. FIG. 1 shows the straight mode in a prior art three-to-two rotary blade folder 10 with a rotating box cam 20 for moving the pins. The cam makes a xc2xd rotation for every one third revolution of the pins and the cam followers. Pins 1, 2 and 3 are connected to and activated by cam followers 11, 12 and 13, respectively, and thus rotate together about the axis of the folder, although the cam followers 11, 12, 13 generally lag the pins 1, 2, 3 a few degrees due to the structure of the connection. The cam follower 11, 12, 13 and rotating cam 20 movement is displayed underneath the folder 10 for clarity. When a cam follower 11, 12 or 13 meets one of two raised sections 21 or 22 in the rotating box cam, the respective pin 1, 2 or 3 is retracted. Thus in section A of FIG. 1, pin 3 is retracted when cam follower 13 meets raised section 21. Signature 100 thus is released by pin 3, is tucked and folded by folding rolls 30. In section B, when raised section 22 (traveling faster than follower 12) and follower 12 meet, pin 2 is retracted as a next signature 101 is released, tucked and folded. In section C, pin 1 is retracted when follower 21 meets raised section 21. Next signature 102 is thus released by pin 1. In section D, pin 3 is again retracted, this time raised section 22 reaching follower 13. The cam followers may include two parallel rollers running in associated grooves slightly offset from one another.
To switch over to a collect mode, an operator disengages one of the tucking blades, stops the machine and physically removes one of the raised cam sections 21, 22 and replaces it with a non-raised section. Because the box cam and the cam follower are moving, it has generally not been possible to permit automatic switching between the collect and straight modes.
FIG. 2 shows a prior art collect mode with section 22 raised section removed and replaced by a non-raised section 23. In Section I of FIG. 2, pin 2 does not retract as a signature 104 passes by the folding rollers 30, because cam follower 12 is met by non-raised section 23 which does not actuate the pin 2. One of the tucking blades, which has be deactivated by another mechanism, also does not tuck. Thus signature 104 remains on the folder 10, as a signature 105 previously did. As shown in Section II, signature 105 thus is joined by a new second signature 106, as cam follower 11 reaches raised section 21. Pin 1 thus releases the lead edge of signatures 105 and 106. The two signatures 105, 106, properly collected, then are tucked by the activated tucking blade, and folded by folding rolls 30. As shown in Section III, signature 107 remains held by pin 3 on folder 30 since non-raised section 23 passes by cam follower 13. Signature 104 is joined by a new signature 108, which together then are folded when the signatures 104 and 108 are tucked. Pin 2 at the same time retracts as cam follower 12 and raised section 21 meet in Section IV. The collect action thus continues in this fashion.
The switch-over from a straight to a collect run using the box cam as shown in FIGS. 1 and 2 however is time-consuming and complicated. An operator manually switches the components, e.g. replaces raised section 22 with non-raised section 23. Moreover, if the parts do not fit properly or are misplaced, valuable time can be lost.
U.S. Pat. No. 5,797,319 purports to disclose a drive device for a folder in a printing press having a folding blade mounted to a folding blade shaft. A drive gear drives a folding blade shaft gear. The drive device also includes a plunger having an intermediate gear between the gear of the folding blade shaft and the drive gear, and a device for moving the plunger between a first longitudinal position and a second longitudinal position. In the first longitudinal position, the intermediate gear meshes with the folding blade shaft gear, whereas in the second longitudinal position, the intermediate gear is out of register with the drive gear. The drive device may also include a cam and an indexing ring operable in response to axial movement of the plunger. During the outward movement of the plunger caused by a helical spring, the cam race is contacted by the pin causing the cam index to rotate. Rotation of the cam permits further outward axial translation of the plunger, because the pin slidably engages different portions of the cam race as the pin continues to rotate. A first stop in the cam race corresponds to the plunger being in the first longitudinal position, and a second stop in the cam race corresponds to the plunger being in the second longitudinal position.
The device of the ""319 patent does not address the problem of prevent pins from retracting during a changeover, but rather only seems to address the tucking motion. Moreover, the device requires a complex arrangement of parts.
Commonly-assigned U.S. Pat. No. 6,093,139 (which is not necessarily prior art to the present application) purports to disclose a product cutting device for flat material. A first and second cam follower assigned to a respective first and second cam move a lever and a further lever about a first and second pivot axis. By the first cam, a product seizing element is moved upon the surface of a cylinder in a direction opposite to the direction of rotation. A further lever assigned to the second cam opens and closes the product seizing element. The folder can, for example, be run in straight mode and/or collect mode. The arrangement of the ""139 patent appears to require that the cam be altered to move between collect and straight modes.
An object of the present invention is to provide a simplified device and method for switching a folder from straight to collect mode.
The present invention provides a folder including:
a cam having a cam follower path and a movable segment, the movable segment having a first actuating part and a second part, the first actuating part and the second part being selectively movable into the cam follower path;
at least one cam follower in the cam follower path; and
at least holding device for holding an edge of a signature, the holding device being actuated by the at least one cam follower.
The folder advantageously permits for easy changes between a collect mode and a straight mode in a rotary blade folder.
The first actuating part preferably includes a raised section, and the second part preferably is a non-raised curved section having a radius of curvature similar to a main section of the cam follower path.
The cam preferably is a rotating box cam, and the first actuating part preferably includes a raised section and a corresponding cut-out section.
Preferably, the cam has a second raised section which is axially stationary in the cam follower path.
The movable segment advantageously may be slid axially along a cam bracket of the cam. Preferably, a pair of bearings pass through slits in the cam bracket to permit movement of the movable segment with respect to the cam bracket. The bearing may be moved by a cam segment housing which is activated by air cylinders.
The folder may further include at least one holding pin for locking the moveable segment in one of two positions. Preferably, the moveable segment has at least two holes for interacting with one of the at least one holding pins. An air cylinder may actuate and release the holding pin.
The folder preferably is a 3 to 2 rotary blade folder.
The present invention also provides a method for switching a folder from a straight mode to a collect mode, the folder being actuated by a cam, the method comprising the steps of:
moving a movable segment of the cam so that a raised section of the movable segment is in a cam follower path of the cam, so as to permit a straight mode of the folder; and
moving the movable segment of the cam so that a non-raised section of the movable segment is in the cam follower path of the cam, so as to permit a collect mode of the folder.
The moving steps preferably are performed automatically using air cylinders.
The method preferably includes the step of locking the movable segment in one of the collect mode and the straight mode using a holding pin.
The moving steps preferably are accomplished by an axial sliding motion of the movable segment.
The present invention also provides a method for operating a rotary blade folder comprising the steps of:
moving a cam follower about a cam follower path of a cam;
releasing and holding leading edges of signatures on the rotary blade folder as a function of the cam follower moving on the cam follower path; and
moving a movable segment of the cam through an actuating device so as to alter the cam follower path and switch the rotary blade folder from a straight mode to a collect mode.